Hard tip pilot bit



March 17, 1959 v G. A. M. PETERSEN 2,

HARD TIP PILOT BIT Filed March 29, 1956 2 Sheets-Sheet 1 50. I 77'- a L7 GINVENTOR.

5-4 1 K 25 GERALD AM PETERSEN 53 @5 37 27 BY l 3| H/S ATTORNEYS M h 7, 1959 G. A. M. PETERSEN 2,877,985

HABD TIP PILOT BIT Fu d March 29, 1956 2 Sheets-Sheet 2 INVENTOR. GERALD A. M. PE TERSEA/ BY H/S 4 7' TOPNEVS United States Patent Ofice Patented Mar. 17, 1959 HARD TIP PILOT BIT Gerald A. M. Petersen, Santa Clara, Calif.

Application March 29, 1956, Serial No. 574,759

9 Claims. (Cl. 255-61) This invention relates to earth boring tools and more particularly to a hardened tipped pilot bit for drilling through rock and other hard material.

The present invention is best used in conjunction with .earth boring angers and is particularly adapted for connection to the leading end of such angers. In the present disclosure I have shown my new pilot bit in combination with a boring head similar to that described and claimed in my .U. S. Patent No. 2,578,014 dated December 11, 1951.

The hard tipped pilot bit of the present invention is interchangeable with the cone shaped pilot bit described and disclosed in my copending application, Serial No. 414,007 filed March 4, 1954 which issued as Patent No. 2,773,673 on December 11, 1956. In other words, both pilot bitsfit the same adapter. provided at the end of the drill shaft. While the cone shaped pilot bit is suitable for opening up a boring in loose or semi-hard surface or subsurfaces, the hardened tipped pilot bit of the present invention is particularly useful when encountering rockor concrete, or when perma frost conditions exist.

The pilot bit of the present invention has as its primary object to cut a leading hole into rock axially of the drill rod and to progressively enlarge such central hole. i It is another object of this invention to provide a drill f tip for a pilot bit in which a slicing action occurs in breaking up rock formation encountered.

,.Another object is. to provide a pilot bit of the afore mentioned character with .hardened cutting, inserts so countering .face is set so far in advance of a radial line from the axis of the drill as to minimize a direct per- Pendicular thrust and to afford a slicing action between The cutting face edge and the material encountered "shank are offset in a leading direction relative to a radial line to present the hardened leading face and inner side face of said cutting inserts for cutting action. In this connection it will be understood that the hardened inserts of the present invention are disposed on shelves afforded in the main body of the pilot bit so that the leading and inner perpendicular faces of each insert is disposed angularly relativeto the circumferal direction of its swing or movement while turning with the drill shaft. In addition to'the foregoing each insert is spaced slightly outwardly from the axis about which it turns .or swings so that no pivotal action relative to hard rock at such axis can occur. Since the leading face of each insertis well in advance of aradial line the inside face of each insert will also afford a slicing action against ,rockat axial centerto chip the same out.

'Thes'e and other-objects and advantages of the present invention will become more apparent from a reading of the following description in the light of the accompanying dawings in which:

Fig. 1 is an elevational view of a boring head having the hardened tipped pilot bit of the present invention associated therewith.

Fig. 2 is a bottom plan (worms eye) view of the boring head and pilot bit of Fig. 1 turned with respect to the same.

Fig. 3 is an enlarged elevational view of the only of Fig. 1.

Fig. 4 is a top plan view of the pilot bit of Fig. 3 taken from line 4-4 therein.

Fig. 5 is a bottom plan view of the leading end of the pilot bit of Fig. 3 at greater scale than shown therein and as seen from line 55 thereof.

Fig. 6 is a fragmentary side elevation of the leading end only of the pilot bit of Fig. 3 as seen from line 6-6 thereof.

Fig. 7 is a section through the leading end of the pilot bit'of Fig. 3 and taken along line 7-7 thereof.

Fig. 8 is a side elevational view of a secondary cutting blade on the pilot bit of the present invention, Fig. '8 being taken substantially along line 8-8 of Fig. 3. v

In the drawings, the boring head 10 shown includes a drill shaft 11 having its upper end 12 adapted for connection to a drive shaft (not shown) for turning movement about the axis of shaft 11. The boring head 10 also includes radial arms 13 and 14 upon which shank plates 15 and 16, respectively, are secured. These shank plates 15 and 16 are each provided with several shanks upon which individual cutting teeth are press fit. The boring head 10 may be as shown in United States Patent No. 2,578,014 wherein all teeth are disposed to encounter earth substantially perpendicular to their are of movement. The boring head 10 also includes an adapter 18 at its lower end. This adapter 18 is preferably similar to the drive lug for pilot bits as shown in my copending application, Serial No. 468,620, filed November 15, 1954. The pilot bit illustrated in my foregoing applications is for use in semi-hard earth. However, when rock, oreandother resistant materials are encountered it be comes necessary to use a pilot bit having hardened cutting tips. Such a hardened tipped pilot bit is shown at '20 in Figs. 1, 2 and 3 and is detailed in Figs. 4 to 8 inclusive.

The pilot bit 20 has a main body 21 which is cast of iron into a shape having an enlarged upper end 22 which conforms substantially in diameter to the drill shaft 11. This enlarged upper end 22 is provided with a socket 23 conforming to the conventional lug on the adapter 18 so that the pilot bit is removable for replacement or interchange.

The main body 21 is further shaped to provide a shaftlike drill tip 24 of slightly lesser diameter than the enlarged socketed upper end 23 of the pilot bit. This shaft-like drill tip 24 projects downwardlyand terminates in a lower end which is of ovoid contour in one diametric direction. As seen in Figs. 3 and 5 the lower end of the drill tip has a kerf 25 milled out alongthe diametric direction a of the ovoid contour mentioned above. In addition thereto the lower end of the drill tip is milled down in certain zones so as to leave a pair of diametrically disposed buttresses 26 and 27.

It should here be noted that the kerf 25 and the other milled out areas of the tip 24 present a flat surface 28 a short distance up from the extreme end of the'tip 24. Each buttress 26 and 27 is preferably less than a quadrant of the round shaft-like tip when the tip is pilot bit at the deepest side of its ovoid contour. Moreover, this ,vance of each rock cutting insert 32.

leading surface 30 is spaced rearwardly from a radial 'line r struck from the axis of the drill shaft 24. In the present disclosure there being but two buttresses and i they being diametrically disposed, the radial lines 1' are diametrically extended in a direction transverse to the and 27. Each of these inserts 32 is also secured. to the milled surface 28 adjacent the respective leading surfaces 30 of the two buttresses.

These tungsten carbide steel inserts 32-are preferably silver soldered to the surfaces 30 and 28 so as to present a hardened cutting face in front of each buttress.

The inserts 32 are bar stock of a length corresponding to the length of the leading surface 30, i. e., radially of the drill shaft 24, to which they are secured. The upper face 33 and back face 34 of each insert fits snugly against the surfaces 28 and 30, respectively. The lower face 35 of each insert is disposed at a slight angle relative to horizontal. About an 11 angle to horizontal has been found most satisfactory. This angle of 11 places the lower face 35 of the insert tangentially with respect to the curve or contour of the lower face of the buttress to which the insert is secured.

' Each insert 32 has a leading face 36 which converges with the angularly disposed lower face 35 to provide a cutting edge 37 along the lower foremost corner of the insert 32. The leading face 36 of each insert 32 is disposed an appreciable distance in advance of the radial line r so that the cutting edge 37 affords a relatively slicing action as it swings about the axis of the shaft-like tip 24. This action is depicted by arrows a in Fig. 5. Note here that the direction of any arrow along the cutting edge 37 is perpendicular to a radial line extended from. the axis of the tip 24.

In connection with the foregoing each insert 32 has an inside face 38 aligned with the trailing or side surface 31 of the buttress to which it is secured. In this manner the inside face 38 of each insert is set back from the diametric axis along the kerf 25. Thus it will be seen that a slight void is provided between the inserts 32 on the tip 24. However, in each case the inside face 38 extends far enough in advance of radial liner to also afford a sweeping or slicing action relative to hard rock encountered at the axis of the tip 24.

By thus spacing the inside faces 38 of the inserts 32 from each other there is no likelihood that the hard ened pilot bit will pivot on hard rock at the axis of the tip 24. On the contrary the forwardly extending portions of the inside faces 38 on the inserts 32 chip or break out any rock formation remaining at the axis of the drill shaft 24 after the cutting edges 37 on'the two inserts have cut around such rock formation.

The shaft-like tip 24 is further configurated to provide a flute-like, vertically extending recess 40 in ad- This flute-like recess 40 as best seen in Figs. 3 and commences at a flat face 41 extending vertically upward from the leading face 36 of the insert 32. As seen in Fig. 5 the recess 40 is formed in that quadrant of the shaft-like tip just in advance of the insert 32. Cross sectionally the leading face 42 of each recess 40 is concave to afford ample space in advance of the cutting insert 32 to allow for removal, i. e., upward passage of spoil chipped out by the cutting edges 37 and inside faces of the inserts 32.

Each recess 40 extends upwardly in the shaft-like tip 24 and terminates in a cove 43 formed substantially midway between the lower and upper ends of the pilot bit 20. This cove 43 is a continuation of the concave face 42 4 and curves outwardly therefrom so as to direct the spoil away from the hole being bored by the tip 24.

A radially extending wing 50 is formed integrally with the main body 21 adjacent each recess 40 formed therein. These wings 50 as illustrated in Figs. 4, 5, 6 and 8 each comprise a spiral-like projection having a radially disposed leading face 51 beginning at the outer extremity of the fiat face 41 on the trailing side of the recess 40 with which it is associated. To put it another way, the leading face 51 of each wing 50 commences in a line vertically above the outer extremity of the insert 32 beneath it and extends radially from the shaft-like tip 24.

The lower, foremost corner 52 of the wing 50 is disposed at the upper end of the full recess 40. That is to say, the corner 52 is at a horizontal plane substantially aligned with the beginning of the cove 43 at the upper end of the recess 40.

A hardened tungsten carbide steel insert, comparable to the ones already explained, is embedded in the lower foremost corner 52 of each wing 50. Rather than repeat the bar type insert of rectangular cross section as shown at 32 in Figs. 6 and 7, I have shown an insert 53 of triangular cross section in connection with the wings 50, Figs. 8 and 6. The arrangement is the same in that the lower face 54 of the insert 53 is disposed at substantially 11 relative to horizontal and the cutting edge 55 is aligned with the leading face 51 of the wing or buttress against which the insert is secured.

From the foregoing it will be appreciated that the cutting edges 55 on the fore corners of the wings 50 cut into rock or material being drilled outside the initial hole bored by the tip 24. In this manner the relatively small hole initially cut is gradually enlarged by the cutting edges on the wings so that the remaining rock later encountered by the individual cutting teeth 17 of the boring head will be easily chipped away thereby The wings 50 as before stated are substantially spirally arranged on the main body 11 of the pilot bit. Each wing 50 occupies substantially one quadrant (Fig. 4) relative to the axis of the pilot bit 20. Each wing has an upwardly spirally tending upper surface 56 so disposed as to receive spoil passing upwardly in the adjacent recess 40. Thus it will be seen that the spoil directed outwardly at the coved upper end 43 of each recess is transferred to the spiral upper surface 56 of the adjacent wing.

While I have described my new hardened tipped pilot bit in specific detail it will be appreciated by those skilled in the art that it is susceptible to variation, alteration and/or modification without departing from the spirit of my invention. I therefore desire to avail myself of all variations, alterations, and/or modifications as fairly come within the purview of the appended claims.

What I claim as new and desire to protect by Letters Patent is:

1. In a pilot bit adapted to be secured to the leading end of a drill shaft of an anger for initially cutting through rock and the like comprising a main body having its lower end terminating in a shaft-like tip of reduced diameter, a vertically extending recess formed within diametrically opposite quadrants of said shaftlike tip to provide segmental buttresses each having a leading face substantially in advance of and parallel to a radial line struck from the axis of said tip, said segmental buttresses having their lower ends curved upwardly and away from the lower end of said shaft-like tip in a direction transverse to said leading face of each said buttress, and a hardened steel insert embedded in the fore corner of each said buttress having its leading face aligned with the leading face of said buttress and its lower face disposed at an anglev upwardly from its leading face and tangential of the adjacent curved lower end of said buttressto form a cutting edge on said insert in adva'nce-ofsaid radial line to afford a slicing secured to the leading end of a drill shaft of an auger boring head for initially drilling through rock and the like, a drill tip comprising a shaft-like tip of reduced diameter relative to said drill shaft having vertically extending recesses formed within diametrically opposite quadrants thereof to provide segmental buttresses thereon, each said segmental buttress having a leadingface substantially in advance of'and parallel to a radial line struck from the axis of said tip, and a hardened steel insert in the fore corner of each said buttress with its leading face aligned with the leading face of said buttress.

3. In a pilot bit including a main body adapted to be secured to the leading end of a drill shaft of an anger boring head for initial drilling through rock and the like, a drill tip comprising a shaft-like tip of reduced diameter relative to said drill shaft having vertically extending recesses formed within diametrically opposite quadrants thereof to provide segmental buttresses thereon, each said segmental buttress having a leading face substantially in advance of and parallel to a radial line struck from the axis of said tip, and a hardened steel insert in the fore corner of each said buttress with its leading face aligned with the leading face of said buttress and its lower face disposed at an angle upwardly to form a cutting edge on said insert in advance of said radial line to afford a slicing action against rock encountered by each said cutting edge.

4. A pilot bit for the leading end of the drill shaft of a boring head for initially drilling through rock and the like comprising a main body having its upper end adapted to be secured to the leading end of said drill shaft and its lower end terminating in a shaft-like tip of reduced diameter, said shaft-like tip having a lower end of ovoid contour in one diametric direction milled out in that direction to leave semi-round buttresses, each said semi-round buttress having a vertically extending recess formed on its leading side to provide diametrically opposed segmental buttresses each having a leading surface disposed in advance of a diametric line transverse to said diametric direction, a hardened steel insert embedded in each said segmental buttress with its leading surface aligned with the leading face of the segmental buttress to which it is attached, each said hardened steel insert having a lower edge disposed substantially tangent to the ovoid contour of the lower end of the segmental buttress to which it is secured and converging with the leading face on said insert to provide a cutting edge substantially in advance of said diametric line to afford a slicing action against rock encountered by said cutting edges.

5. A pilot bit for the leading end of the drill shaft of an anger boring head for initially drilling through rock and the like comprising a main body having its upper end adapted to be secured to the leading end of said drill shaft and its lower end terminating in a shaft-like tip of reduced diameter, said shaft-like tip having an ovoid contour in one diametric direction and having a kerf formed therein along said diametric direction to provide semi-round buttresses on each side of said kerf, a vertically extending recess formed in the leading portion of each said semi-round buttress to present a segmental buttress with a leading face substantially in advance of a diametric line transverse to said diametric direction, a hardened steel insert embedded in the leading face of each said segmental buttress with its leading face aligned with the leading face of said buttress and parallel to said diametric line to afford a slicing action against rock encountered by said cutting edge, each said insert having a forwardly moving inside face aligned with the trailing face of said segmental butangle from the lower edge of the leading surface of said buttress towhich it is connected and a leading face disposed in advance ofsaiddiaimetri line to afford a slicing tress'tq which it is secured for'breaking out unbored material encountered at the axis of said tip. 1

6. A pilot bit for the leading end of the drill shaft 0 an auger boring head for initially drilling through rock and the like, comprising a main body having an upper end secured to the leading end of said drill shaft and its lower end terminating in a shaft-like tip of reduced diameter, a vertically extending recess formed within diametrically opposed quadrants of said shaft-like tip affording passage for spoil and to provide diametrically opposed segmental buttresses on said tip each having a leading face in advance of a diametric line extended from the axis of said shaft-like tip, a hardened steel insert secured against the leading face of each said segmental buttress having a lower face disposed at a downward action against rock encountered by said cutting edge, and a radially extending wing formed integrally with said main body adjacent each said recess formed therein, each said wing beginning midway up said main body with its leading face disposed to receive spoil from the upper end of an adjacent recess, and a hardened steel cutting insert embedded in the lower leading corner of each said wing.

7. A pilot bit for the leading end of the drill shaft of an auger boring head for initially drilling through rock and the like, comprising a main body having its upper end secured to the leading end of said drill shaft and its lower end terminating in a shaft-like tip of reduced diameter, said shaft-like tip having its lower end of ovoid contour in one diametric direction, a vertically extending re cess formed in said shaft-like tip in each quadrant thereof to provide segmental buttresses in the leading surface of each of which is in advance of a diametric line transverse to said diametric direction, each said segmental buttress being of less than quadrantal proportion at its extreme end, a hardened steel insert embedded against the leading surface of each said less than quadrantal buttress with its leading face aligned with the leading surface on the segmental buttress to which it is attached, each said insert having a lower face disposed tangent to the ovoid contoured lower end of the buttress to which it is connected converging with the leading face of said hardened steel tip to present a cutting edge in advance of said diametric line for slicing action against rock encountered thereby.

8. A pilot bit for the leading end of the drill shaft of an auger boring head for initially drilling through rock and the like, comprising a main body having its upper end secured to the leading end of said drill shaft and its lower end terminating in a shaft-like tip of reduced diameter, said shaft-like tip having its lower end of ovoid contour in one diametric direction, a vertically extending recess formed in said shaft-like tip in each quadrant thereof to provide segmental buttresses in the leading surface of each of which is in advance of a diametric line transverse to said diametric direction, each said segmental buttress being of less than quadrantal proportion at its extreme end, a hardened steel insert embedded against the leading surface of each said less than quadrantal buttress with its leading face aligned with the leading surface on the segmental buttress to which it is attached, each said insert having a lower face disposed tangent to the ovoid contoured lower end of the buttress to which it is connected converging with the leading face of said hardened steel tip to present a cutting edge in advance of said diametric line for slicing action against rock encountered thereby, and a radially extending cutter wing formed integrally with said main body adjacent each recess formed in said shaft-like tip, each said cutter wing beginning in a cutter edge at the upper extremity of said recesses and having its leading face disposed to receive spoil therefrom.

9. A pilot bit for the leading end of the drill shaft of and the like, cornprising' a main body having its upper end secured to the leading end of said drill shaft and its lower end terminating'in a shaft-like tip of reduced diameter,

"said shaft-like tip having its lower end of ovoid contour in one diametric direction, a vertically extending recess formed in said shaft-like tip in each quadrant thereof to provide segmental buttresses in the leading surface of each of which is in advance of a diametric line transverse to said diametric direction, each said segmental buttress being of less than quadrantal proportion at its extreme end, a hardened steel insert embedded against the leading surface of each said less than quadrantal buttress with 'its leading face aligned with the leading surface on the segmental buttress to which it isattached, each said insert having a lower face disposed tangent to the ovoid contoured lower end of the buttress to which it is connected converging with the leading face of said hardened steel tip to present a cutting edge in advance of said .diametric lineifor sliding action against rock encountered thereby, and a radially extending wing formed'intcg-rally with said main body adjacent each recess formed in said shaft-like tip, each said Wing beginning at the upper extremity of said recesses and having its leading face disposed to receive spoil therefrom, and a hardened steel cutting insert embedded in the lower leading corner of each said wing. r

References Cited in the file of this patent UNITED STATES PATENTS 2,634,104 Clayton et al. Apr. 7, 1953 15 2,770,449 McCarthy Nov. 13', 1955 FOREIGN PATENTS 606,371 Great Britain Aug. 12, 1948 

